This invention relates to voltage regulators and, more particularly, to a low-power voltage regulator with negative temperature coefficient. Features of the system disclosed in the present application are also disclosed and claimed in copending application Ser. No. 908,336 filed May 22, 1978, by Steven E. Marum for Integrated Injection Logic Electronic System with Voltage Regulator for Multiplexed Liquid Crystal Display, which application is assigned to the assignee of the present application.
Present-day electronic systems having liquid crystal display, such as calculators, timepieces and the like, use a liquid crystal material which is sensitive to ultraviolet light, thereby necessitating the use of a yellow-colored ultraviolet filler over the display. These displays are used because the temperature coefficients of the threshold and saturation voltages are nearly zero which is very compatible over the operating temperature ranges with the battery voltage utilized in the system. Multiplexed liquid crystal displays, which do not require ultraviolet filtering, have considerable temperature coefficients at the threshold and saturation voltages and cannot be used unless the battery voltage is regulated to match them. Ordinary voltage regulators utilize a zener diode with positive temperature coefficient to provide for a resultant temperature coefficient of nearly zero. In order to provide a voltage regulator circuit with negative temperature coefficient, the circuit would be required to include a plurality of diodes having a negative temperature coefficient connected in series. However, the resulting circuit would draw a considerable amount of wasted current through the added diodes.
It is therefore an object of the present invention to provide a low-power voltage regulator for driving a negative temperature coefficient liquid crystal display.
It is another object of the present invention to provide a low-power voltage regulator which operates most efficiently in combination with integrated injection logic circuitry.
A further object of the invention is to provide an improved electronic integrated injection logic system with liquid crystal display.
It is yet another object of the invention to provide a low-power voltage regulator having a negative temperature coefficient.
Still a further object of the invention is to provide an electronic system, such as an electronic timepiece, with a liquid crystal display which does not require ultraviolet filtering.